Timepiece mechanism provided with a magnetic gear

Abstract

The present invention discloses a mechanism (1) comprising a magnetic gear (2) comprising a first wheel (6A) and a second wheel (6B), the first wheel (6A) having a first permanent magnet pole (7) forming a first magnetic tooth system (8), and the second wheel (6B) having a second magnetic tooth system (10) made of ferromagnetic material, the first wheel (6A) and the second wheel (6B) being arranged such that the first magnetic tooth system (8) has a first magnetic coupling with the second magnetic tooth system (10); the magnetic gear (2) further comprises a third wheel (6C) having a second permanent magnet pole (9) forming a third magnetic tooth system (12), the third wheel (6C) and the second wheel (6B) being arranged such that the third magnetic tooth system (12) has a second magnetic coupling with the second magnetic tooth system (10); the magnetic gear (2) is arranged such that at any given time, the first wheel (6A) and the third wheel (6C) are each angularly positioned in a specific manner.

Description

Technical Field

[0001] This invention relates to the field of magnetic gears formed by a first wheel and a second wheel that are magnetically meshed with each other.

[0002] Specifically, the present invention relates to mechanisms incorporating such magnetic gears, particularly timekeeping mechanisms. The invention also relates to timepieces including such mechanisms. Such timepieces can be, in particular, wristwatches. Background Technology

[0003] Magnetic gears are known devices that can be used to transmit mechanical torque between two parts without any direct contact between them, and therefore without causing wear or friction. Such gears offer the following benefits:

[0004] - Since there is no mechanical wear on some of the teeth, no oil or lubricant is required;

[0005] - The toothed parts can interact and transmit torque and mechanical energy, even when they are sealed apart; and

[0006] - The toothed portion can be used to limit the maximum torque, and thus can help avoid damage, such as in the event of a mechanical shock.

[0007] Such magnetic gears typically comprise two wheels that are magnetically meshed with each other. The first wheel has first permanent magnet poles, which are usually alternated and arranged in a circular pattern, defining a first magnetic tooth system. For example, these first magnetic poles are defined by a bipolar magnet having radial and preferably alternating magnetization. The second wheel has teeth or second magnetic poles made of a soft ferromagnetic material, which are defined, for example, by a bipolar magnet also having alternating polarity, arranged in a circular pattern, defining a second magnetic tooth system. The first and second wheels are usually located in the same general plane, although superimposed tooth systems are possible when they are both formed by permanent magnetized poles. The magnetic coupling between the tooth systems of the first and second wheels means that when one of these first and second wheels is driven to rotate, the other wheel is also driven to rotate. Thus, mechanical torque is transmitted in the magnetic gear, which generally corresponds to the function of a gear.

[0008] However, one drawback of this type of magnetic gear is that the maximum mechanical torque that can be transmitted between the two gears (without gear slippage or sliding) is limited by various factors. Therefore, magnetic gears with a higher maximum transmittable mechanical torque are needed.

[0009] To this end, an intuitive solution involves using wheels with larger tooth diameters and minimizing the distance between the two wheels. However, the magnetic interaction intended to occur between the teeth of the two wheels prevents any possibility of providing a sufficiently narrow gap between adjacent teeth on either of the two wheels. Making the distance between the two tooth sets so short that they do not contact each other would create real problems in terms of tolerances. Within the scope of this invention, two main problems associated with magnetic gears have been identified. The first main problem stems from the fact that a positioning torque (parasitic magnetic torque) is periodically applied to the rotating drive wheel. The term "magnetic torque" is understood to mean a magnetic couple. The positioning torque to be overcome is a phenomenon stemming from the fact that a minimum energy exists in a magnetic gear when the two wheels have two aligned corresponding teeth. The positioning torque operates to place the two wheels in a position with minimum energy. In operation, it therefore periodically opposes the rotation of the drive wheel. This parasitic magnetic torque can be very high, possibly as high as (or even higher than) the mechanical torque that can be transmitted between the two wheels of the magnetic gear. To overcome this destructive torque, the motor driving one of the two wheels must be able to provide a much larger torque than the mechanical torque transmitted in the magnetic gear, which unnecessarily increases the motor's power consumption. In any case, and assuming the first wheel is the driving wheel and the second wheel is driven by the first, the transmittable mechanical torque may not be limited by the magnetic interaction between the wheels, but by the minimum mechanical torque originating from the first wheel. In the typical magnetic gear considered here, the mechanical torque provided by the first wheel must be equal to the maximum positioning torque (parasitic magnetic torque) plus the mechanical torque that will be transmitted in / through the magnetic gear.

[0010] The second important problem addressed by this invention is that the maximum mechanical torque that can be transmitted in the aforementioned typical magnetic gear is limited by the magnetic torque modulation that occurs therein during the operation of the magnetic gear. More specifically, as the two wheels rotate, their two corresponding magnetic gear systems alternately pass from a first case to a second case, in which the teeth of one of the two magnetic gear systems are aligned along an axis passing through the center of the two wheels, and in which in the second case, two adjacent teeth of that magnetic gear system are in a symmetrical angular position relative to this axis passing through the center of the two wheels. Between the first and second cases, a decrease in the magnetic torque applied to the driven wheel by the driving wheel is observed, and therefore a change in the maximum mechanical torque that can be transmitted in the gear is observed. Thus, the maximum mechanical torque transmitted in the gear is limited by the minimum magnetic torque that occurs between the rotation of the two wheels. Summary of the Invention

[0011] Therefore, the object of the present invention is to overcome the disadvantages of the prior art described above by providing a mechanism (especially a timekeeping mechanism) that includes magnetic gears in the mechanism that are easy to manufacture and install (especially with regard to the manufacture of the magnetic gear system and relative positioning tolerances), and which makes it possible to increase the maximum mechanical torque that can be transmitted in the gears (in which one gear does not slip relative to the other).

[0012] For this purpose, the present invention relates to a mechanism, particularly a timekeeping mechanism, comprising a magnetic gear including a first wheel and a second wheel. The first wheel has a first permanent magnet pole arranged to form magnetized teeth of a first magnetic tooth system, from which a first magnetic flux of alternating polarity originates. The second wheel has teeth made of a soft ferromagnetic material defining a second magnetic tooth system. The first and second wheels are arranged such that the first magnetic tooth system has a first magnetic coupling with the second magnetic tooth system generated by the first magnetic flux, the first magnetic flux temporarily polarizing the teeth of the second magnetic tooth system in the form of magnetic attraction. These teeth are temporarily located in the first magnetic coupling region with the first magnetic tooth system, and thus the first magnetic flux from the first magnetic flux passes through these teeth, causing the first and second wheels to magnetically mesh with each other. The magnetic gear defines a first reference half-axis that begins from the axis of rotation of the second wheel and intercepts the axis of rotation of the first wheel. According to the invention, the magnetic gear further includes a third wheel, the third wheel having second permanent magnet poles arranged to form magnetized teeth of a third magnetic gear system, with second magnetic fluxes of alternating polarities emerging from the magnetized teeth of the third magnetic gear system. The third wheel and the second wheel are arranged such that the third magnetic gear system has a second magnetic coupling with the second magnetic gear system generated by the second magnetic flux, the second magnetic flux temporarily polarizing the teeth of the second magnetic gear system in the form of magnetic attraction: these teeth are temporarily located in the second magnetic coupling region with the third magnetic gear system, and thus the second magnetic flux from the second magnetic flux passes through these teeth respectively, such that the second wheel and the third wheel are magnetically meshed with each other, the magnetic gear defining a second reference half-axis that starts from the axis of rotation of the second wheel and cuts off the axis of rotation of the third wheel. A given angle Φ exists between the first reference half-axis and the second reference half-axis. The first permanent magnet pole of the first wheel (and thus the magnetized tooth / magnetic gear system) has a first phase relative to the first reference half-axis, and the second permanent magnet pole of the third wheel (and thus the magnetized tooth / magnetic gear system) has a second phase relative to the second reference half-axis. The magnetic gears are arranged such that the phase shift between the first wheel and the third wheel, defined as the difference between the first and second phases, remains constant. The angle Φ and the phase shift are selected to substantially determine the value of the maximum mechanical torque that can be transmitted without slippage in the magnetic gears (i.e., without slippage between the second wheel and the first and third wheels).

[0013] The corresponding phases of the first and third rounds, i.e., the phases of the first and second permanent magnet poles (i.e., the corresponding magnetized teeth of the first and third magnetic tooth systems), at a given moment are defined by the angle of one of these permanent magnet poles (one of these magnetized teeth) relative to the first and second semi-axis axes, modulo the angular period of the first and third magnetic tooth systems (i.e., the angular distance between two adjacent magnetized teeth of the magnetic tooth system), divided by the angular period and multiplied by 360°. The phase shift is given by the difference between the two phases. It should be noted that the phase shift β is equal to the phase shift β‒360°. Therefore, its value depends on the instantaneous values ​​of the two phases under consideration changing in either direction from β to β‒360°. A constant phase shift is maintained (e.g., a phase shift equal to 90° and a phase shift equal to ‒270° define an identical phase shift such that a phase shift whose value varies between these two values ​​is a constant phase shift).

[0014] Typically, providing a third gear equipped with permanent magnet poles and magnetically coupled to the second gear in a magnetic gear allows for the selection of the maximum mechanical torque that can be transmitted in the gear without slippage by fully selecting the angle Φ and the phase shift for this purpose. Specifically, the third gear allows for an increase in the maximum mechanical torque that can be transmitted in the magnetic gear without slippage (in other words, without disengagement in the kinematic connection provided to the gear, i.e., in the magnetic meshing between the second gear and the first and third gears) for a given motor torque. This advantage stems from the fact that the maximum total magnetic torque in the magnetic gear is based on the angular offset α between the first and third gears and on the significant change in the phase shift between the first and third gears. The angular offset α is defined as equal to the aforementioned angle Φ, modulo the period P2 of the magnetic gear system of the second gear. Furthermore, such a magnetic gear with two gears (which have magnetized teeth magnetically coupled to each other, and which have teeth made of ferromagnetic material) provides a greater mechanical torque to keep all gears stationary, regardless of the angular position of the gears when stationary. This is particularly advantageous in the case of dynamic, finite inertia mechanisms.

[0015] Preferably, by selecting the angle Φ and phase shift between the first and third gears, the maximum transmittable mechanical torque in the magnetic gears (i.e., without one gear slipping on the other) is more than twice the corresponding maximum mechanical torque that can be transmitted by another magnetic gear consisting only of the first and second gears. More specifically, for the maximum transmittable mechanical torque, each of the first and third gears is limited by the minimum magnetic torque between that gear and the second gear, based on the angular position of either of the two gears, which determines the maximum mechanical torque that can be transmitted from one gear to the other. However, when the first and third gears have a sufficiently selected angular offset and phase shift, an offset is seen between the two minimum values ​​of the two corresponding magnetic torques, such that the minimum value of the two magnetic torques added together (total magnetic torque) can be more than twice the minimum value of only one of the two magnetic torques. This property is significant.

[0016] In a favorable alternative, the first and third magnetic gear systems each comprise the same number N1 teeth, and the first and third wheels are angularly positioned relative to the rotation axis of the second wheel in such a manner that the angle Φ satisfies the mathematical relation:

[0017]

[0018] Where N2 is the number of teeth in the second magnetic gear system (10) and N is a positive integer less than N2. This range of values ​​for angle Φ(N) yields good results in terms of the maximum transmittable mechanical torque of the gears (for certain ranges of phase shift between the permanent magnet poles of the first and third gears, respectively, which are associated with the values ​​of the range).

[0019] Preferably, the value of the angle Φ(N) is chosen to be substantially equal to

[0020]

[0021] The optimal value of angle Φ(N) yields the best results in terms of the maximum transferable mechanical torque of the gear (for certain ranges of phase shifts between the permanent magnet poles of the first and third gears, as defined below for the optimal phase shift). Generally, for certain values ​​of phase shift between the permanent magnet poles of the first and third gears, the optimal value of angle Φ(N) provides a maximum transferable mechanical torque that is more than twice the maximum transferable mechanical torque provided by another gear consisting only of the first and second gears.

[0022] In another advantageous alternative, the first and third magnetic gear systems each further include the same number N1 teeth, with two specific teeth belonging to each of these systems having a given constant angular difference Ψ relative to the respective first and second semi-axis axes. The first and third wheels are positioned at an angle relative to the respective first and second semi-axis axes such that the angular difference Ψ satisfies the mathematical relationship stated above.

[0023]

[0024] Where M is a positive integer less than N1, which depends on two specific teeth, namely the teeth selected to measure the angular difference. This range of angular difference Ψ(M) yields good results in terms of the maximum transmittable mechanical torque of the gears (for certain ranges of angular offset between the first and third gears, respectively, associated with the values ​​of the range).

[0025] Preferably, the value of the angle difference Ψ(M) is chosen to be substantially equal to

[0026]

[0027] The optimal value of the angular difference Ψ(M) yields the best results in terms of the maximum transmittable mechanical torque of the gears (for a specific range of angular offsets between the first and third gears corresponding to the optimal angle Φ(N) for all N). Typically, for certain values ​​of the angular offsets of the first and third gears, this optimal value of Ψ(M) provides the maximum transmittable mechanical torque, which is more than twice the maximum transmittable mechanical torque provided by another gear consisting only of the first and second gears. The angular phase shift is defined as the angular difference Ψ(M), modulo the period of the first gear train (equal to the period of the third gear train). Therefore, the angular phase shift δ is the same for all M. Similarly, the angular offset α mentioned above is the same for all N. The combination of the preferred / optimal angular offset α corresponding to the optimal angle Φ(N) for all N and the preferred / optimal angular phase shift δ corresponding to the preferred / optimal angular difference Ψ(M) for all M yields the best results in terms of the maximum transmittable mechanical torque.

[0028] According to an exemplary embodiment of the invention, the first wheel and the third wheel are substantially disposed on either side of the second wheel, so that the second wheel is substantially arranged between the first wheel and the third wheel. This balances the magnetic radial force acting on the second wheel.

[0029] In a favorable alternative, the first and third wheels are the drive wheels, and the second wheel is driven.

[0030] According to an exemplary embodiment of the present invention, the corresponding magnetized teeth of the first tooth system and the third tooth system are arranged such that the first magnetic flux and the second magnetic flux respectively emerge from these magnetized teeth in a principal direction, the principal direction being radial relative to the corresponding rotation axes of the first wheel and the third wheel.

[0031] According to a first specific embodiment, the mechanism further includes two motors, preferably two Lavet motors, the rotors of each of which are kinematically connected to a corresponding wheel in the first and third wheels to drive the corresponding wheel to rotate, the two motors being configured to drive the first and third wheels at least partially simultaneously.

[0032] According to a second specific embodiment, the mechanism further includes a motor, preferably a Lavet motor, whose rotor is kinematically connected to the first and third wheels to drive them to rotate, the first and third wheels being mechanically coupled, in particular via a gear train.

[0033] Advantageously, the first and third wheels have the same diameter and each has a tooth system with the same number of teeth, and the distance between the two wheels is greater than four times their diameter, preferably greater than eight times their diameter. This effectively eliminates any parasitic magnetic interaction between the first and third wheels.

[0034] Preferably, the first and third wheels each have a central portion made of ferromagnetic material, around which their first and second permanent magnet poles are arranged in pairs with an equal number of complementary magnetic poles, thereby forming a bipolar magnet. The bipolar magnet has radially magnetized teeth that respectively define the magnetized teeth of the first and third magnetic tooth systems. This allows the magnetic field lines between adjacent bipolar magnets to be effectively closed via the respective central portions of the first and third wheels.

[0035] Advantageously, the second wheel includes a rim that forms a continuous circular base of the second magnetic tooth system, the continuous circular base extending from the rim and being made of a soft ferromagnetic material to form a closure for the magnetic circuits of the first and second magnetic fluxes passing through the second tooth system.

[0036] According to one specific exemplary embodiment of the present invention, the first, second, and third wheels are coplanar. According to another specific exemplary embodiment of the present invention, the first, second, and third wheels may extend in different planes.

[0037] Advantageously, for each of the first and third wheels, the mechanism further includes a soft ferromagnetic element or group of soft ferromagnetic elements arranged relative to that wheel to generate a magnetically compensating torque to compensate, at least substantially compensate, the magnetic positioning torque, which is individually subjected to by each of the first and third wheels and is generated by the magnetic coupling of that wheel with the second magnetic gear system of the second wheel. The magnetic positioning torque has a periodic intensity variation based on the angular position of the associated wheel relative to the reference half-axis, which originates from and truncates the rotational axis of the second wheel. The ferromagnetic element or group of ferromagnetic elements is advantageously arranged to generate the magnetically compensating torque, which also has a periodic intensity variation based on the angular position of the associated wheel relative to the reference half-axis associated with that wheel, and the magnetically compensating torque and the individual magnetic positioning torque preferably have a 180° phase shift.

[0038] The presence of such a configuration of soft ferromagnetic elements, or groups of such elements, effectively overcomes to a large extent the problem of magnetic positioning torque experienced by each of the first and third gears by eliminating most of this parasitic torque and thus minimizing the overall positioning torque experienced by the second gear and the first and third gears together. More specifically, for each of the first and third gears, when they are the drive wheels in the magnetic gears, variations in magnetic coupling result in variations in the mechanical torque provided by the motor device. The presence of such ferromagnetic elements, or groups of such ferromagnetic elements, thus allows for a reduction in the magnitude of this variation in each of the first and third gears without having any significant effect on the magnetic coupling in the magnetic gears. In other words, the mechanical torque to be "smoothed" to the first and third gears hardly alters the variation in magnetic coupling between the second gear and the first and third gears, a variation that depends on the angular position of the second gear relative to the corresponding magnetic poles of the first and third gears; according to the invention, the arrangement of the magnetic gears significantly compensates for this final variation.

[0039] It should be noted that, due to the angular offset α and phase shift (described above) provided between these first and third wheels, the magnetic gear according to the invention also allows for a significant reduction in the total positioning torque through the arrangement of the first and third wheels. More specifically, with regard to the advantageous alternative arrangement of the angular offset α and phase shift, and more specifically, the optimal values ​​identified for these two parameters, the second wheel experiences two out-of-phase magnetic positioning torques generated by the first and third wheels respectively, such that the total positioning torque experienced by the second wheel is much lower than in the prior art, i.e., without the third wheel. Specifically, when the first and third wheels are integrated with each other so that they rotate together, the two wheels as a whole also experience a lower positioning torque, which is therefore essentially equal to the overall positioning torque applied to the second wheel. Thus, the magnetic gear according to the invention effectively solves the two main problems identified in the prior art embodiments described in the background, enabling the magnetic gear to transmit large mechanical torques in a stable and safe manner with lower motor torque.

[0040] The present invention further relates to timepieces, particularly wristwatches, which include the mechanism of the present invention. Attached Figure Description

[0041] The objectives, advantages, and features of the mechanism according to the invention will become more apparent in the following description of various non-limiting embodiments illustrated with reference to the accompanying drawings, wherein:

[0042] Figure 1 This is a top view of a mechanism incorporating magnetic gears according to a particular alternative embodiment of the present invention;

[0043] Figure 2 It is similar to the first embodiment of the mechanism according to the present invention. Figure 1A top view shows that the magnetic gear mechanism consists of two small wheels and one larger wheel;

[0044] Figure 3A It is a collection of graphs showing different values ​​of angular offset of the two smaller wheels relative to the axis of rotation of the larger wheel. These graphs represent... Figure 2 The evolution of the maximum mechanical torque that can be transmitted in a magnetic gear, based on the angular phase shift between the two small wheels of the mechanism;

[0045] Figure 3B It is a collection of graphs showing different values ​​of the angular phase shift between two small wheels, representing a graph based on... Figure 2 The evolution of the maximum mechanical torque that can be transmitted in the magnetic gears due to the angular offset between the two small wheels of the mechanism;

[0046] Figure 4A It is shown Figure 2 A graph showing the evolution of the optimal angular phase shift of the two small wheels in the mechanism (based on the angular offset between the two small wheels);

[0047] Figure 4B Is with Figure 4A A similar graph to the one shown, which represents Figure 2 The evolution of the optimal phase shift (in a scale of zero to one) of the two pinions in the mechanism (based on the offset between the two pinions (also in a scale of zero to one)), and the region of these two parameters that give the relatively high maximum mechanical torque transmitted in the magnetic gear.

[0048] Figure 5 This is a top view of a first alternative embodiment of the mechanism of the present invention;

[0049] Figure 6 yes Figure 5 A sectional view of the mechanism taken along the cutting plane VI-VI;

[0050] Figure 7 This is a top view of a second alternative embodiment of the mechanism of the present invention;

[0051] Figure 8 yes Figure 7 A sectional view of the mechanism taken along cutting plane VIII-VIII; and

[0052] Figure 9 This is an enhanced alternative to the second embodiment of the mechanism according to the invention. Figure 5 A view similar to the one in the middle. Detailed Implementation

[0053] Figure 1A specific alternative embodiment of mechanism 1 according to the invention is shown, particularly a timepiece-type mechanism, which includes a magnetic gear 2 to illustrate the general concept of the invention. The invention provides a magnetic gear 2 comprising two wheels, particularly smaller diameter wheels with dimensions specific to the pinion, each wheel having permanent magnet poles arranged circularly around the rotation axes 32, 38 of the respective wheel. These two wheels are magnetically coupled to another wheel 6B, particularly a larger diameter wheel, which is equipped with teeth made of a soft ferromagnetic material with relatively high permeability. The two smaller wheels are driving wheels and the larger wheel is driven, or vice versa. Figure 1 In this design, each of the two smaller wheels is formed by a single rotating element 5A, 5C, which is formed by a circular bipolar magnet 5A, 5C (in disk form) having a central axis of rotation 32, 38 perpendicular to the magnetic axis of the bipolar magnet. It should be noted that the bipolar magnet can have another shape, particularly a rectangular shape. Each bipolar magnet 5A, 5C generates a magnetic field that couples to the larger wheel 6B in a corresponding region of this larger wheel, defining a corresponding magnetic coupling region with the corresponding rotating bipolar magnet. The two rotating bipolar magnets 5A, 5C thus each magnetically engage with wheel 6B, which is preferably a larger diameter wheel, advantageously positioned between the two bipolar magnets. Each rotating bipolar magnet 5A, 5C generates a magnetic flux that allows temporary and local magnetic polarization of the magnetic tooth system of wheel 6B.

[0054] Therefore, the magnetic field generated by each of the rotating bipolar magnets 5A and 5C produces local and temporary magnetization on wheel 6B. More specifically, in the teeth of wheel 6B made of the soft ferromagnetic material, these teeth are in an active state at a given moment, i.e., they are temporarily located in the magnetic engagement region, which is defined according to the magnetic coupling region between wheel 6B and the associated bipolar magnet. The number of permanent magnet poles required to generate this local magnetization for each wheel shown by the rotating elements 5A and 5B is reduced to at least two magnetic poles forming the bipolar magnet.

[0055] The magnetic gear 2 defines a first reference half-axis 30, which begins from the rotation axis 34 of the larger diameter wheel 6B and cuts off the first of the two smaller wheels (in... Figure 1 The rotation axis 32 (shown by the first rotating bipolar magnet 5A) is defined by the magnetic gear 2. The magnetic gear 2 also defines a second reference half-axis 36, which begins from the rotation axis 34 of the wheel 6B and cuts off the second pinion (in...). Figure 1 The rotation axis 38 (shown by the second rotating bipolar magnet 5B) is between the first reference half-axis 30 and the second reference half-axis 36, with a given angle Φ. Figure 1 As shown, the angle Φ separating the first reference half-axis 30 and the second reference half-axis 36 is measured from the second reference half-axis 36.

[0056] like Figure 2 and Figures 5 to 9 As shown, the magnetic gear 2 includes three wheels 6A, 6B, and 6C. Generally, the first wheel 6A and the third wheel 6C, which are smaller in diameter than the second wheel 6B, each have N1 permanent magnet poles 7 and 9, arranged in a circle and respectively defining the first magnetic gear system 8 and the third magnetic gear system 12. Preferably, as Figure 2 and Figures 7 to 9 In this configuration, the first wheel 6A and the third wheel 6C are substantially positioned on either side of the second wheel 6B, thus the second wheel 6B is substantially arranged between the first wheel 6A and the third wheel 6C. Preferably, the first wheel 6A and the third wheel 6C are drive wheels, and the second wheel 6B is driven by these two wheels to rotate. The three wheels 6A, 6B, and 6C may be coplanar or extend in separate planes.

[0057] N1 permanent magnet poles 7 and 9 form the corresponding magnetized teeth of the first magnetic tooth system 8 and the third magnetic tooth system 12, from which alternating first and second magnetic fluxes emerge, respectively. Since the magnetic poles are arranged in a circular manner with alternating polarization, there is an even number of these poles. Preferably, the number N1 is an even number between four and ten, including both four and ten. The corresponding magnetic poles 7 and 9 of the first wheel 6A and the third wheel 6C are typically arranged in pairs with the same number of complementary magnetic poles, which are positioned around the central portions 32 and 38 of the axes forming the wheels 6A and 6C, or located in openings through which such axes pass. These pole pairs thus form bipolar magnets that define the corresponding magnetized teeth of the first magnetic tooth system 8 and the third magnetic tooth system 12 by their outer magnetic poles. In the case where multiple bipolar magnets have radial magnetization, the central portions 32 and 38 are advantageously made of ferromagnetic material or manganese alloy material. This material effectively seals the magnetic field lines originating from the inner poles of multiple bipolar magnets, particularly between adjacent bipolar magnets, via the corresponding central portions of the first round 6A and the third round 6C. Figure 2 and Figures 5 to 9 In the specific exemplary embodiment shown, each of the first wheel 6A and the third wheel 6C includes six bipolar magnets 7 and 9 that respectively form six magnetized teeth of the first magnetic tooth system 8 and the third magnetic tooth system 12. Preferably, as shown Figure 2 , 5 As shown in 7 and 9, the corresponding magnetized teeth 7 and 9 of the first tooth system 8 and the third tooth system 12 are arranged such that the first magnetic flux and the second magnetic flux appear from these magnetized teeth 7 and 9 in the main direction, which is radial relative to the corresponding rotation axes of the first wheel 6A and the third wheel 6C, so that the bipolar magnet is radially magnetized.

[0058] The second wheel 6B has N2 teeth made of a soft ferromagnetic material, which define the second magnetic tooth system 10. The second wheel 6B includes an annular rim made of a magnetic material, typically a soft ferromagnetic material, from which forty-two teeth, also made of soft ferromagnetic material, emerge, forming the second magnetic tooth system 10. This annular rim thus forms a continuous circular base of the second magnetic tooth system 10, through which the magnetic circuits of the first and third interacting magnetic fluxes provided by the first magnetic tooth system 8 and the third magnetic tooth system 12 are closed.

[0059] At any given time, one of the permanent magnet poles 7A of the first gear 6A has a first angular position relative to the first reference half-axis 30, and one of the permanent magnet poles 9A of the third gear 6C has a second angular position relative to the first reference half-axis 36. The magnetic gears 2 are arranged such that the first gear 6A and the third gear 6C are always angularly positioned relative to their respective reference half-axiss, such that the first angular position and the second angular position have a constant angular difference Ψ. Angles Φ and Ψ are typically chosen to determine the value of the maximum mechanical torque that can be transmitted in the magnetic gears without the risk of slippage. Specifically, angles Φ and Ψ are advantageously chosen such that the maximum mechanical torque that can be transmitted in the magnetic gears 2 without the possibility of slippage is more than twice the corresponding maximum mechanical torque that can be transmitted by another magnetic gear consisting only of the first gear 6A and the second gear 6B. This will be described below. Figures 3A to 4B These values ​​for angles Φ and Ψ are shown.

[0060] In a favorable alternative, round 6A and round 6C are positioned at an angle relative to round 6B, such that angle Φ satisfies the following mathematical relationship (1):

[0061] (1)

[0062] Where N is a positive integer less than N2 (therefore N is any integer between 1 and N2-1, i.e. N = 1, 2, ..., N2-1).

[0063] This choice of angle Φ is the result of several simulations, which specifically provide... Figure 3A The different curves C1, C2, C3, C4, and C5 plotted in the figure are represented based on the angular phase shift δ=Ψ(M)-Ψ. M-1 For the angular offset α=Φ(N)-Φ N-1 The evolution of the maximum mechanical torque (e.g., %) that can be transmitted in the magnetic gear 2 with different values. The magnetic period P2 of the second gear 6B is defined as equal to 360° / N2, and the magnetic period P1 of each of the first gear 6A and the third gear 6C is defined as equal to 360° / N1. Angle Φ N-1 Limited to equal to And the angle Ψ M-1 Limited to equal to Where M is a positive integer less than N1 (therefore M is any integer between 1 and N1‒1, i.e., M = 1, 2, ..., N1‒1). The angular offset α is included in Φ. N-1 and Φ N Between, where Φ N It equals N·P2, and the angular phase shift δ is included in Ψ. M-1 and Ψ M Between, where Ψ M It equals M·P1. Therefore, the angular offset α equals Φ(1). The mathematical relation (1) is equivalent to the angular offset relation P2 / 3≤α≤2·P2 / 3.

[0064] Curves C1, C2, C3, C4, and C5 represent the evolution of the maximum mechanical torque (e.g., %) that can be transmitted in magnetic gear 2 based on the angular phase shift δ when the angular offset α is equal to zero, P2 / 4, P2 / 3, P2 / 2, and 2P2 / 3, respectively. Curves C3 and C5 are chosen for the lower and upper bounds of the previous mathematical relation (1) and the equivalent relation described above. As can be seen from curves C2, C3, C4, and C5, for certain ranges of angular phase shift, the maximum mechanical torque that can be transmitted in magnetic gear 2 without slippage is more than twice the corresponding maximum mechanical torque that can be transmitted by another magnetic gear consisting only of the first gear 6A and the second gear 6B. A good symmetry between curves C3 and C5 with respect to the midpoint angular phase shift P1 / 2 can be seen, which is easily explained because the two cases are magnetically equivalent for the magnetic gears. This explains why mathematical relation (1) has lower and upper bounds corresponding to the lower and upper angular offsets positioned at the same distance from the midpoint angular offset. The best results were obtained for the C4 curve corresponding to the midpoint angle offset P2 / 2.

[0065] Preferably, and given that Figure 3A (And especially curve C4, which gives the best results for certain values ​​of the angular phase shift in terms of maximum transferable mechanical torque), choose the value of angle Φ(N) such that it is essentially equal to This corresponds to a midpoint angle offset of P2 / 2. More specifically, the highest maximum transmittable mechanical torque is obtained for the combination of midpoint angle offset P2 / 2 and midpoint angle phase shift P1 / 2.

[0066] exist Figure 1 In the specific case shown, N1 is eighteen and the number of teeth N2 of the second magnetic tooth system 10 is forty-two, and the angle Φ(18) is preferably equal to 150 degrees. Figure 2 In the specific case shown, N is twenty-one and the number of teeth N2 of the second magnetic tooth system 10 is forty-two, and the angle Φ(21) is preferably equal to 175.7 degrees. Figure 3AAs shown in the fourth curve C4, for the number of teeth N1 of the first magnetic gear system 8 and the third magnetic gear system 12, which are equal to six teeth, the preferred value of the angular phase shift δ (based on the maximum transmittable mechanical torque of gear 2) is near the optimal value of 30 degrees (this latter value of the optimal angular phase shift δ is denoted as Ψ). opt 4).

[0067] In the favorable alternative, and independently of the preceding mathematical relation (1) (in other words, when starting by choosing the value of angle Φ before the value of angle Ψ), the first round 6A and the third round 6C are respectively angularly positioned to the corresponding semi-axis 30 and 36, such that the angle difference Ψ satisfies the following mathematical relation (2):

[0068] (2)

[0069] exist Figure 3B Different curves C6, C7, C8, C9, and C10 are plotted, which are represented based on the angular offset α=Φ(N)-Φ N-1 For the angular phase shift δ=Ψ(M)-Ψ M-1 The evolution of the maximum mechanical torque (e.g., %) that can be transmitted in the magnetic gear 2 with different values. It should be noted that the angular phase shift δ is equal to Ψ(1). The mathematical relation (2) is equivalent to the relation of angular phase shift P1 / 3≤δ≤2·P1 / 3.

[0070] Curves C6, C7, C8, C9, and C10 represent the evolution of the maximum mechanical torque (e.g., %) that can be transmitted in magnetic gear 2 based on angular offset when the angular phase shift is equal to zero, P1 / 8, P1 / 4, 3P1 / 8, and P1 / 2, respectively. As can be seen from curves C9 and C10, for certain ranges of angular offset, the maximum mechanical torque that can be transmitted in magnetic gear 2 without slippage is more than twice the corresponding maximum mechanical torque that can be transmitted by another magnetic gear consisting only of the first gear 6A and the second gear 6B (where curve C10 obtains the best results for the midpoint angular phase shift P1 / 2).

[0071] Preferably, and given that Figure 3B (And especially curve C10, which gives the best results for certain values ​​of angular offset in terms of maximum transmittable mechanical torque), choose the angular difference Ψ(M) such that it is essentially equal to This corresponds to the optimal angular phase shift δ = P1 / 2. Therefore, in Figure 2 In the specific case shown, where M is "1" and the number of teeth N1 of the first magnetic tooth system 8 and the third magnetic tooth system 12 is equal to "6", the angle Ψ(1) is preferably equal to 30 degrees. This corresponds to the optimal angular phase shift δ = 30°. Figure 3BAs shown in curve C10, for the number of teeth N2 of the second magnetic gear system 10, which is equal to “42”, the preferred value of the angular offset α (based on the maximum transmittable mechanical torque of gear 2) is near the optimal angular offset P2 / 2, which is approximately 4.286 degrees.

[0072] Figure 4A The corresponding figure is shown graphically. Figure 3A The four points Ψopt2, Ψopt3, Ψopt4, and Ψopt5, corresponding to the abscissas of the peak values ​​of curves C2, C3, C4, and C5 (i.e., corresponding to the optimal angular phase shift), represent different values ​​of the angular offset α corresponding to these four curves. It should be noted that in... Figure 4A In this study, a quasi-linear function is obtained for the optimal angular phase shift based on the angular offset. The theoretical curve is a linear line D1, which indicates that for the angular offset X·P2 within the period P2 of the magnetic gear system of the second wheel 6B (where X is between 0 and 1), the optimal angular phase shift is X·P1 within the period P1 of the magnetic gear system of the first wheel 6A and the third wheel 6C. Therefore, a relationship exists on this theoretical line D1. .

[0073] Figure 4B Gives a comparison with Figure 4A The graphical representation is similar, but with a different scale for the coordinates: a curve based on the angular phase shift divided by period P1 (i.e., δ / P1) and a curve based on the angular offset divided by period P2 (i.e., α / 2). In addition to the curve connecting various optimal values, this... Figure 4B The figure also shows the value coupling region Z1, for which a maximum mechanical torque substantially greater than two that can be transmitted in a magnetic gear is obtained. The figure can be read as follows: once either angular phase shift or angular offset is selected, the advantageous range of one of these two parameters lies on either side of the optimal value of the other parameter, within a specific range of values ​​that vary depending on the other parameter.

[0074] In the following description, elements indicated by the same reference numerals are similar. Without limiting this to the scope of the invention, mechanism 1 is preferably a timekeeping mechanism.

[0075] The following will refer to Figure 2 A first embodiment of a mechanism 1 including a magnetic gear 2 according to the present invention is described. According to this first embodiment of mechanism 1, mechanism 1 includes two motors (for clarity, these two motors are...) Figure 2 (Not shown in the diagram). The first round 6A, the second round 6B, and the third round 6C extend in the same global plane.

[0076] The corresponding rotors of the first motor and the second motor are kinetically connected to the first wheel 6A or the third wheel 6C, respectively, to drive the wheel to rotate. For example, each motor is a Lavet motor with a reducer gear. The two motors are configured to drive the first wheel 6A and the third wheel 6C simultaneously. More specifically, the two motors are configured to drive the first wheel 6A and the third wheel 6C simultaneously, such that the first angular position and the second angular position are permanently kept out of phase by an angle Ψ(M) defined by the mathematical relation (2) given above. In this first embodiment of mechanism 1, the first wheel 6A and the third wheel 6C are drive wheels in the magnetic gear 2.

[0077] The following will refer to Figures 5 to 9 A second embodiment of the mechanism 1 according to the invention, including a magnetic gear 2, is described. According to this second embodiment of mechanism 1, the mechanism includes a single motor (not shown in the figures for clarity). A first wheel 6A, a second wheel 6B, and a third wheel 6C extend in the same general plane. The first wheel 6A and the third wheel 6C are generally mechanically coupled via a gear train 14 and driven by the motor to rotate them. Preferably, and as... Figures 5 to 9 As shown, the first wheel 6A and the third wheel 6C have the same diameter and the same number of teeth in their respective magnetic tooth systems. The distance between the first wheel 6A and the third wheel 6C is advantageously greater than four times the diameter of each of the two wheels, and preferably greater than eight times that diameter.

[0078] The motor rotor is kinematically connected to at least one of the first gear 6A and the third gear 6C, or to a complementary gear belonging to the gear train 14, so as to simultaneously drive these first and third gears to rotate. The motor is preferably a Lavet motor or a continuously rotating clock motor.

[0079] According to the first alternative embodiment of the second embodiment of mechanism 1, such as Figure 5 and Figure 6 As shown, the motor rotor is connected to a gear train 14 (which mechanically couples the first gear 6A and the third gear 6C) to simultaneously drive both the first and third gears to rotate. The gear train 14 is connected to shafts 20A, 20C of each of the first gear 6A and the third gear 6C for the mechanical coupling of these gears. According to... Figure 6In the example shown, gear train 14 consists of three wheels 22A, 22B, and 22C; for example, the central wheel 22B is connected to the motor and mechanically couples the other two wheels 22A and 22C. The central wheel 22B is mounted on a central shaft 20B. Each of the other two wheels 22A and 22C is coaxially mounted on a corresponding shaft 20A or 20C of one of the first wheel 6A and the third wheel 6C. A pin 24 placed on the side of mechanism 1 allows bridge 26 to be connected to plate 28. In this first alternative of the second embodiment, the first wheel 6A and the third wheel 6C are drive wheels in magnetic gear 2. In another alternative, the second wheel is the drive wheel and the first and third wheels are driven.

[0080] like Figure 7 and 8 The second alternative of the second embodiment of the illustrated mechanism 1 differs substantially from the first alternative in two main aspects. First, the first wheel 6A and the third wheel 6C are separated from each other as much as possible to limit the magnetic interaction between them. They are arranged substantially on either side of the second wheel 6B (the larger wheel), i.e., they are substantially aligned with the diameter of the second wheel. Therefore, the radial magnetic force acting on the second wheel 6B is advantageously substantially balanced. Second, the mechanism 1 includes a pivot bearing for the wheel 22B of the gear train 14, which is aligned with the axis of rotation 34 of the second wheel 6B and carried by the central portion of the second wheel 6B, which has no bearing of its own on the gear 22B side.

[0081] An improved alternative to the first alternative according to the second embodiment of mechanism 1, such as... Figure 9 As shown, for each of the first wheel 6A and the third wheel 6C, mechanism 1 further includes ferromagnetic elements 40A and 40C, which are arranged relative to the wheel 6A and 6C to optimally compensate for and counteract the parasitic magnetic torque (at least for most) experienced by the wheel 6A and 6C individually. More specifically, as described above, each of the first drive wheel 6A and the third drive wheel 6C experiences a parasitic magnetic torque (referred to as positioning torque).

[0082] Ferromagnetic elements 40A and 40C are preferably arranged in the overall plane of the first wheel 6A and the third wheel 6C, respectively, which is the same as the overall plane of the second wheel 6B. The ferromagnetic elements 40A and 40C include two ends 43 and 44 extending toward the corresponding magnetic tooth systems 8 and 12 of the first wheel 6A and the third wheel 6C, respectively. Typically, each of the ends 43 and 44 forms an angle with respect to the first reference semi-axis 30 and the second reference semi-axis 36, the value of which is substantially equal to (J... (1 / 2)·360 / N1, i.e. (J =1 / 2)·P1, where J is an integer "1" and N1 is different for each end. It should be noted that in a more complex alternative, in addition to the two ends, other protrusions may be provided, each positioned at a different angle among a plurality of angles defined by the value J between "1" and "N1" in the above mathematical formula. The intermediate portion 46 connects the two ends 43, 44. The intermediate portion 46 has a semi-circular shape that extends in the overall plane of the first wheel 6A and the third wheel 6C (on the side opposite to the second wheel 6B). It should be noted that the dimensions of the intermediate portion 46 are designed to generate low magnetic torque on the first wheel 6A and the third wheel 6C, respectively, which is much lower than the individual magnetic positioning torque and magnetic compensation torque, generated integrally by the ferromagnetic elements 40A and 40C and mainly generated by the two ends 43 and 44, which are arranged to face inward relative to the circle defined by the intermediate portion 46 toward the corresponding tooth trains 8 and 12 of the first wheel 6A and the third wheel 6C.

[0083] Ferromagnetic elements 40A and 40C are respectively arranged to generate magnetic compensation torque, the period of which is the same as the periodic variation of the intensity of the parasitic magnetic torque, based on the angular positions of the first wheel 6A and the third wheel 6C relative to the first reference half-axis 30 and the second reference half-axis 36, respectively. Advantageously, as shown, the magnetic compensation torque and the parasitic magnetic torque (positioning torque) have a phase shift of approximately 180°. Preferably, ferromagnetic elements 40A and 40C are respectively configured such that the maximum intensity (amplitude) of the magnetic compensation torque is substantially equal to the maximum intensity (amplitude) of the magnetic positioning torque.

[0084] According to the improvement, ferromagnetic elements 40A and 40C are respectively configured in such a manner to generate magnetically compensated attractive forces as a whole on the first wheel 6A and the third wheel 6C, respectively. These magnetically compensated attractive forces are aligned with the first reference semi-axis 30 and the second reference semi-axis 36, respectively, and their direction is opposite to the direction of the radial magnetic attractive force exerted as a whole on the first wheel 6A and the third wheel 6C by the second wheel 6B. It should be noted that... Figure 9 The alternative shown already possesses a small magnetically compensated attraction generated by the semi-circular intermediate portion, but this intermediate portion primarily serves to form a low-resistivity magnetic circuit between the two ends 43 and 44, and its magnetic attraction to the first wheel 6A and the third wheel 6C is much smaller than the radial magnetic attraction exerted by the second wheel 6B on the first wheel 6A and the third wheel 6C, respectively; these two attraction forces are not of the same order of magnitude. Different specific embodiments can be considered to achieve this improvement, particularly by wisely selecting the two values ​​of the aforementioned parameter J and / or by adding a third portion facing inward toward the wheel under consideration and / or by configuring the intermediate portion differently.

[0085] It should be noted that although this configuration including ferromagnetic elements 40A and 40C has been described with reference to the first example of the second embodiment of mechanism 1, this configuration is equally applicable to the first embodiment and the second alternative of the second embodiment of mechanism 1, while remaining within the scope of the invention.

[0086] As an example and in a non-limiting manner, the inventors have obtained, in numerical form, the results for the maximum mechanical torque that can be transmitted in gear 2. These figures were obtained for a number of teeth N1 equal to six and for a number of teeth N2 equal to forty-two. For another magnetic gear consisting only of the first gear 6A and the second gear 6B, the maximum mechanical torque that can be transmitted in the gear is equal to 93 µNm. For the magnetic gear 2 according to the invention, for an angular offset value α equal to zero degrees and for an angular phase shift value δ equal to zero degrees, the maximum mechanical torque that can be transmitted in gear 2 is equal to 186 µNm. This value corresponds exactly twice to the value obtained for the magnetic gear consisting only of the first gear 6A and the second gear 6B, which is expected. For an optimal angular offset value α equal to 4.286 degrees and an optimal angular phase shift value δ equal to 30 degrees, the maximum mechanical torque that can be transmitted in gear 2 is approximately equal to 227 µNm (which corresponds to an increase of more than 20% compared to the case where α = δ = 0°).

Claims

1. A timepiece movement comprising a magnetic gear (2) comprising a first wheel (6A) and a second wheel (6B), the first wheel (6A) being provided with first permanent magnetic poles arranged to form magnetized teeth of a first magnetic train (8) from which first magnetic fluxes with alternating polarity emerge respectively, the second wheel (6B) being provided with teeth made of soft ferromagnetic material defining a second magnetic train (10), the first wheel (6A) and the second wheel (6B) being arranged so that the first magnetic train (8) has a first magnetic coupling with the second magnetic train (10) generated by the first magnetic fluxes, the first magnetic fluxes temporarily polarizing in the form of magnetic attraction the teeth of the second magnetic train (10) that are temporarily located in the first magnetic coupling area with the first magnetic train (8) and that are therefore crossed respectively by a first magnetic flux from among the first magnetic fluxes, so that the first wheel (6A) and the second wheel (6B) are magnetically engaged with each other, the magnetic gear (2) defining a first reference half-axis (30) starting from the rotation axis (34) of the second wheel (6B) and intercepting the rotation axis of the first wheel (6A); characterized in that, The magnetic gear (2) further comprises a third wheel (6C) provided with second permanent magnets arranged to form magnetized teeth of a third magnetic train (12) from which second magnetic fluxes with alternating polarity respectively emerge, the third wheel (6C) and the second wheel (6B) being arranged so that the third magnetic train (12) has a second magnetic coupling generated by the second magnetic fluxes with the second magnetic train (10), the second magnetic fluxes temporarily polarizing, in the form of magnetic attraction, the teeth of the second magnetic train (10) that are temporarily located in the second magnetic coupling area with the third magnetic train (12) and therefore respectively pass through the teeth from the second magnetic fluxes so that the second wheel (6B) and the third wheel (6C) are magnetically engaged with each other, the magnetic gear (2) defining a second reference half-axis starting from the rotation axis of the second wheel (6B) and intercepting the rotation axis of the third wheel (6C), between the first reference half-axis and the second reference half-axis there being a given angle Φ; wherein the first permanent magnets of the first wheel (6A) have a first phase with respect to the first reference half-axis and the second permanent magnets of the third wheel (6C) have a second phase with respect to the second reference half-axis, the magnetic gear (2) being arranged so that the phase shift between the first wheel and the third wheel, defined as the difference between the first phase and the second phase, is always constant; and wherein the angle Φ and the phase shift are selected so as to determine the value of the maximum mechanical torque that can be transmitted in the magnetic gear without slippage occurring between the second wheel and the first wheel and the third wheel.

2. A timepiece movement according to claim 1, characterised in that, The angle Φ (N) and the difference between the first phase and the second phase are selected so that the maximum mechanical torque that can be transmitted without slippage is more than double the corresponding maximum mechanical torque that can be transmitted by another magnetic gear comprising only the first wheel (6A) and the second wheel (6B).

3. A timepiece movement according to claim 1, characterised in that, The first magnetic train (8) and the third magnetic train (12) each comprise the same number N1 of teeth (7, 9); and wherein the first wheel (6A) and the third wheel (6C) are angularly positioned with respect to the rotation axis of the second wheel in such a way that the angle Φ (N) satisfies the mathematical relationship: where N2 is the number of teeth in the second magnetic train (10) and N is a positive integer less than N2.

4. Timepiece movement according to claim 3, wherein the value of the angle Φ (N) is selected to be equal to 。 5. A timepiece movement according to claim 1, characterised in that, The first magnetic tooth system (8) and the third magnetic tooth system (12) each comprise the same number N1 of teeth (7, 9), two specific teeth belonging respectively to these first and third magnetic tooth systems always having a given constant angular difference value Ψ with respect to the respective first and second half-axes; and wherein the first wheel (6A) and the third wheel (6C) are angularly positioned with respect to the respective first and second half-axes so that the angular difference value Ψ satisfies the mathematical relationship: where M is a positive integer smaller than N1.

6. Timepiece mechanism according to claim 5, wherein the value of the angular difference value Ψ(M) is chosen to be equal to 。 7. A timepiece movement according to any one of the preceding claims, characterised in that, The respective teeth (7, 9) of the first magnetic tooth system (8) and of the third magnetic tooth system (12) are arranged so that the first magnetic flux and the second magnetic flux respectively emerge from these teeth (7, 9) in a main direction which is radial with respect to the respective rotation axis of the first wheel (6A) and of the third wheel (6C).

8. A timepiece movement according to any one of claims 1 to 6, characterised in that, The first wheel (6A) and the third wheel (6C) are drive wheels and the second wheel (6B) is driven.

9. A timepiece movement according to claim 8, characterised in that, It also comprises two motors, the respective rotors of which are kinematically connected to different ones of the first wheel (6A) and of the third wheel (6C) in order to drive these first and third wheels in rotation so that they rotate, the first and third wheels thus being drive wheels in the magnetic gear (2); and wherein the two motors are configured to be able to drive the first wheel (6A) and the third wheel (6C) at least partially simultaneously.

10. A timepiece movement according to claim 8, characterised in that, The first wheel (6A) and the third wheel (6C) are mechanically coupled; and wherein the mechanism also comprises one motor, the rotor of which is kinematically connected to the first wheel (6A) and to the third wheel (6C) in order to be able to drive these first and third wheels in rotation.

11. A timepiece movement according to claim 10, characterised in that, A gear train (14) mechanically couples the first wheel (6A) and the third wheel (6C), the rotor driving this gear train and the first wheel (6A) and the third wheel (6C) in rotation.

12. A timepiece movement according to any one of claims 1 to 6, characterised in that, The first wheel (6A) and the third wheel (6C) are arranged on either side of the second wheel (6B), the second wheel (6B) thus being arranged between the first wheel (6A) and the third wheel (6C).

13. A timepiece movement according to claim 11, characterised in that, The first wheel (6A) and the third wheel (6C) are arranged on either side of the second wheel (6B), the second wheel thus being arranged between the first wheel and the third wheel; and wherein the gear train (14) consists of three additional wheels, a first additional wheel (22A) and a second additional wheel (22C) of the three additional wheels being connected respectively to the shaft of the first wheel and of the third wheel, a third additional wheel (22B) mechanically coupling the first additional wheel and the second additional wheel; and wherein the timepiece mechanism comprises a guide bearing for the third additional wheel, the guide bearing being aligned with the rotation axis of the second wheel (6B) and being carried by this second wheel.

14. A timepiece movement according to any one of claims 1 to 6, characterised in that, Said first wheel (6A) and said third wheel (6C) have, respectively, a central portion made of ferromagnetic material, on the periphery of which said first permanent magnetic poles and said second permanent magnetic poles thereof are arranged in pairs with as many complementary magnetic poles, respectively, so as to form a dipole magnet having radial magnetization and defining, respectively, the corresponding magnetized teeth of said first tooth system (8) and of said third tooth system (12).

15. A timepiece movement according to any one of claims 1 to 6, characterised in that, Said second wheel (6B) comprises a rim from which emerges a continuous circular base of said second tooth system (10), said continuous circular base being made of soft ferromagnetic material so as to form a closure for the magnetic circuit of said first magnetic flux and of said second magnetic flux passing through the second tooth system.

16. A timepiece movement according to claim 8, characterised in that, For each of said first wheel (6A) and of said third wheel (6C), it further comprises a soft ferromagnetic element or a set of soft ferromagnetic elements arranged with respect to the wheel so as to compensate for a sole magnetic positioning torque, each of said first wheel and of said third wheel being subjected to said sole magnetic positioning torque and said sole magnetic positioning torque resulting from said magnetic coupling of the wheel with said second tooth system (10) of said second wheel (6B), said sole magnetic positioning torque to which each of said first wheel and of said third wheel is subjected having a periodic variation of intensity based on the angular position of the wheel with respect to a reference half-axis, said reference half-axis starting from said rotation axis of said second wheel (6B) and intercepting said rotation axis of the wheel.

17. A timepiece movement according to claim 16, characterised in that, Said ferromagnetic element or set of ferromagnetic elements is arranged so as to generate a magnetic compensation torque, said magnetic compensation torque also having a periodic variation of intensity based on said angular position of the associated wheel with respect to said reference half-axis, said reference half-axis intercepting said rotation axis of the wheel, said magnetic compensation torque and said sole magnetic positioning torque having a phase shift of 180°.

18. A timepiece, characterized in that, Said timepiece comprises a timepiece movement according to any one of the preceding claims.

19. A timepiece according to claim 18, characterised in that Said timepiece is a watch.

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